Device for manufacturing iron or non-ore-smelting type

ABSTRACT

A device for manufacturing iron, in which by supplying an alternating current directly to the accumulation of a preheated iron-manufacturing raw material in the form of powder and particles a high-density current concentrated locally in the accumulation is formed. The reduction of iron oxide is carried out by applying Joule heat and electromagnetic force caused by the high density current to the raw material for manufacturing iron through which the current is flowing, thereby to soften a gangue material and simultaneously to aggregate iron particles, whereby in a non-ore-smelting state the iron in the form of a bare rod or particles is separated from the gangue material in the form of pumice.

United States Patent [1 1 Atsukawa Aug. 14, 1973 DEVICE FORMANUFACTURING IRON OR NON-ORE-SMELTING TYPE [76] Inventor: MasamlAtsukawa, 14-3, 2-chome,

Tsukushino, Machida-shi, Tokyo, Japan [22] Filed: June 17, 1971 [21]Appl. No.: 153,947

Hudson .1: 263/28 x Primary Examiner-Roy N. Envail, Jr. Attorney-E. F.Wenderoth et a1.

[57] ABSTRACT A device for manufacturing iron, in which by supplying analternating current directly to the accumulation of a preheatediron-manufacturing raw material in the form of powder and particles ahigh-density current concentrated locally in the accumulation is formed.The reduction of iron oxide is carried out by applying Joule heat andelectromagnetic force caused by the high density current to the rawmaterial for manufacturing iron through which the current is flowing,thereby to soften a gangue material and simultaneously to aggregate ironparticles, whereby in a non-oresmelting state the iron in the form of abare rod or particles is separated from the gangue material in the fonnof pumice.

I 17 Claims, 22 Drawing Figures Patented Aug. 14, 1973 3,752,897

7 Sheets-Sheet 1 FIG. I

SPECIFIC RESISTANCE flhm. 5

HEW

20 40 60 M TIME Sec.

MASAMI ATSUKAWA,

INVENTOR I BwwmwAi ATTORNEYS Patented Aug. 14, 1973 7 Sheets-Sheet 2FIG. 4

Asc y ATTORNEY Patented Aug. 14, 1973 3,752,897

7 Sheets-Sheet 3 FIG. 8(B)s-|2 MASAMI ATSUKAWA INVENTOR BYlJlZJMATTORNEYS Patented Aug. 14, 1973 .7 Sheets-Sheet 4 MASAMI AISUKAWAINVENTOR ATTORNEY Patented Aug. 14, 1973 '7 Sheets-Sheet 6 MASAMIATSUKAWA INVENTOR Bmmazw,m

ATTORNEY s Patented Aug. 14, 1973 3,752,897

7 Sheets-Sheet 7 FIG. mus) FIG. IO(C) lO-IT lO-l7 MASAMI ATSUKAWA,

INVENTOR BYUMRZMALJM ATTORNEY DEVICE FOR MANUFACTURING IRON ORNON-ORE-SMELTING TYPE BACKGROUND OF THE INVENTION Generally, iron oreused most usually as an ironmanufacturing raw material consists of threekinds of oxides, namely, hematite (Fe O magnetite (Fe O and limonite(2Fe O -3H O).

There are two steps to be carried out in order to produce iron out ofthese oxides: the first step is to separate (to reduce) oxygenchemically combined with iron, and the second step is to separate agangue material mechanically combined with iron (this step is calledSeparation of Iron from Gangue Material). A system employed mostgenerally as the former step, namely, the reduction of the iron ore, isone in which the material for manufacturing iron is heated incombination with material (reducing agent) stronger in affinity thaniron with respect to oxygen. Solid carbon (coke) is most often used as areducing agent.

As for the latter step, that is, the separation of iron from ganguematerial, the iron ore is subjected to both heat to weaken the combiningforce between iron and gangue material and to a force to separate ironfrom gangue material, simultaneously. In conclusion, one of thefundamental elements in manufacturing iron is to apply both heat andforce to the iron ore at the same time.

In the study of a conventional iron-manufacturing system, there has beena tendency to place emphasis on only energy of heat, though it has beenwell known that both energy of heat and force is necessary formanufacturing iron, and the force has been obtained by depending ongravity. Furthermore, the heat necessary for the conventionaliron-manufacturing has been actually ,dependent on primitive combustionheat (manifestive heat).

In other words, it is obvious that the complete smelting of ore isabsolutely required for production of iron as far as it depends ongravity as a separating force. In order to accomplish the completesmelting of ore, required are rich ore, rich coal, or poor ore and coalenriched in advance. At the same time, the smelting point of slag mustbe lowered by preparing gangue material and the combustion temperaturemust be raised by increased air-blowing power. Therefore, raw materialsuitable for the ore-smelting method is exhausted, and consequently thecost of the raw material goes up. Due to these conditions in combinationwith the large scale equipment required for the ore-smelting method, thecost of manufactured iron is greatly raised.

SUMMARY OF THE INVENTION It is accordingly the primary object of thepresent invention to provide a novel device for manufacturing iron whichis acceptable from an industrial view point and is most economical.

Another object of the present invention is to provide a novel device formanufacturing iron, in which iron particles (or iron mass) are separatedfrom gangue material with the aid of Joule heat and electromagneticforce which are produced by feeding an alternating current directly tothe accumulation of an ironmanufacturing raw material in the form ofpowder or particles.

A further object of the present invention is to provide a device formanufacturing iron, in which a tubular electrical rotary kiln comprisinga pre-heating section and an iron-manufacturing section, is inclined androtatably arranged under the condition that the ironmanufacturingsection is placed below the preheating section. A plurality of annularelectrodes which are provided at a mutually proper interval and whichserve to supply an alternating current to the accumulation of a powderyor granular raw material conveyed successively in the iron-manufacturingsection, are provided in the iron-manufacturing section.

A still further object of the present invention is to provide aniron-manufacturing device which comprises a tunnel kiln inside which ametallic endless belt is provided to convey powdery and granular rawmaterial, and a preheating device adapted to heat both the upper andlower surfaces of the thin accumulation of the powdery and granular rawmaterial spread on the endless belt.

A particular object of the present invention is to provide aniron-manufacturing device, in which a plurality of refractory unitcrucibles which are in the form of a rectangular hexahedron with an openplane and which receive a preheated powdery and granular raw material,are arranged to form an endless belt, each of the unit crucibles beingprovided with a pair of movable electrodes cooperating with a pluralityof external electrodes arranged on an externally surrounding structure.Iron granules (or iron mass) are separated from pumice-type. slag (organgue material) in each of the unit crucibles.

The nature, utility, and principle of the invention will be more clearlyunderstood from the following detailed description with reference to theaccompanying drawings.

. BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawings:

FIG. 1 is a graphic diagram illustrating the relationships betweenspecific resistance and temperature when heating an accumulation of apowdery and granular raw material;

FIG. 2 is also a graphic diagram illustrating both the relationshipsbetween time and temperature of the accumulation, and the relationshipsbetween time and a current density flowing through the accumulation of apowdery and granular raw material in the case when a certain voltage isapplied to the accumulation;

FIG. 3 is a diagram explaining the interaction of electromagnetic forcesproduced when a current is made to flow through two conductors placedadjacently;

FIG. 4 is a diagram to illustrate an electromagnetic coagulationaccording to the present invention;

FIG. 5 is a diagram illustrating the process in which iron componentsand other components are successively separated from granular orescontaining iron components, under the electromagnetic coagulationaction;

FIG. 6 is a diagram exhibiting a phenomenon that an attraction force(centripetal force) is imparted to granular ores containing an ironcomponent under electromagnetic coagulation action, according to thepresent invention;

FIG. 7 is a vertical section view of an electrical rotary kiln,according to the present invention, which illustrates the agitationcondition of raw material in the kiln;

FIGS. 8(A) through 8(C) are a longitudinal sectional view, of anembodiment of the present invention, a longitudinal sectional view ofits essential part, and a view sectioned along line VIII VIII in FIG.8(B), respectively;

FIG. 9(A) is a diagram explaining the principle of the invention whenprocessing the accumulation of a powdery and granular raw material fedsuccessively by an endless belt;

FIGS. 9(B) through 9(E) are an elevation view of a section of a unitcrucible which is in the form of a rectangular hexahedron with an openplane and which actually forms the endless belt shown in FIG. 9(A), aplan view of the unit crucible, a sectional view taken along the line IXIX in FIG. 9(3) and a sectional view taken along the line IX IX in FIG.9(C), respec tively;

FIG. 9(F) is a diagram of the accumulation of a powdery and granular rawmaterial shown in FIG. 9(A), which is in pieces extendingperpendicularly to the moving direction of an endless belt;

FIG. 9(G) is a sectional view of a part of the endless belt formed byconnecting the unit crucibles shown in FIGS. 9(B) to 9(E), by usingappropriate hinges at their bottom edge portions; 7

FIG. 10(A) shows another embodiment of the present invention, whichutilizes the unit crucibles shown in FIGS. 9(B) through 9(E); and

FIGS. 10(B) and 10(C) are sectional views taken along the line X X andthe line X X of FIG. 10(A), respectively.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to anovel device for manufacturing iron, in which Joule heat of analternating current directly flowing in the powdery and granular rawmaterial of iron ore is utilized as heatrequired for separation of aniron component and gangue material which are contained in the iron ore,i.e., fora refining process, and an electro-magnetic force based on saidcurrent is utilized as a force for the separation; and further relatesto a device to carry out the method.

It is the most industrial and economical means to reduce an ironcomponent in ore by only heating a mix ture of ore and coke. However, inthis case, the fundamental elements governing the reduction rate and thereduction efficiency are the specific surface area of the raw material,and the conduction rate and conduction efficiency of heat to be given tothe raw material. In addition, the specific surface area of a solidsubstance is inversely proportional to the grain size. Therefore, a masssubstance is the hardest to reduce, while a powdery and granularsubstance is the easiest. Accordingly, it will be apparent that, if heatis appliedat a high rate and a high efficiency up to the center of theaccumulation of the powdery and granular raw material, the most superiorreduction process can be obtained.

As described above, one of the conditions under which the reduction rateand the reduction efficiency are maximized is the fact that the grainsize of the raw material is small," and the other is the fact that heatpenetration is sufticiently appropriate to the raw mate rial." However,as a gas medium, which has the lowest heat conductivity among thecomponent, is interposed in the accumulation of the powdery or granularraw material, the accumulation is extremely low in heat conductivity. 1

Therefore, this is a problem which cannot be solved by the classicalmethod of manufacturing iron in which the manifestive heat is utilized.

On the other hand, it has been found that the electrical resistance ofthe accumulation of the powdery or granular material comprising themixture of substances each of which is negative in the temperaturecoefficient of electrical resistance as found in ceramics, coke, andiron ore comprising various metal oxides, is also negative in thetemperature coefficient, and the absolute value of the negative value isextremely high. Moreover, when the accumulation is heated, theelectrical resistance is prominently lowered and the lowering variationof the electrical resistance is notable in the range of a relatively lowtemperature, as shown in FIG. 1. Therefore, it will be understood that,when the powdery or granular material is subjected to heat, theresistance due to this heating operation is lowered rapidly andconsequently an electric current rapidly passes through the rawmaterial. It is one of the most important and fundamental elements thatthe conductivity of a current with respect to the powdery or granularraw material is increasingly improved by heating the material. Theabove-mentioned current (electron current) cannot pass through theaccumulation of the powdery or granular material at anormal temperature;However, by heating the accumulation, the current can readily passthrough it and collides with atoms and molecules constituting theaccumulation whereby energy of motion possessed by each electron isconverted into energy of heat. In this case, the penetrating rate ofheat in the powdery or granular raw material is equal to the currentconducting rate.

On the contrary to the above description, the combustion heat ormanifest heat employed heretofore shows little penetrating action withregard to the accumulation of the powdery or granular raw material.

This is due to the following reasons: that is, the combustion heat isthe energy of motion of gas molecules (for instance, C0,, H 0, and thelike) which are pro duced by combustion. These. molecules are extremelylarger in size and mass than the electron. Therefore, it is hard for themolecules to; penetrate into the accumulation of the powdery or granularraw material. Accordingly, all the manifest heat collides with thesurface of the accumulation, and is then converted into heat energy onthe surface. Then, the heat energy thus converted is introduced towardsthe inside of the accumulation. However, the substance constituting theaccu-' mulation of the powdery or granular raw material comprisesceramics, coke, and gas filled in the powder and granules thereof any ofwhich are low in heat conductivity. Therefore, the heat conductivity inthe accumulation could be regarded as almost zero.

According to the present invention, Joule heat is produced inside theaccumulation of powdery or granular material by supplying an alternatingcurrent to the accumulation, and the thus produced Joule heat is adaptedto heat the raw material at a high rate and a high efficiency, wherebyboth the reduction rate and the reduction efficiency can be remarkablyimproved.

As apparent from FIG. 1, when the accumulation of the powdery orgranular raw material is heated, the specific resistance of theaccumulation is abruptly lowered. Therefore, it can be anticipated thata current can easily pass through the accumulation if it is pre-heated.The accumulation of the powdery or granular raw material is (1) negativein the temperature coefficient of electrical resistance, (2) very low inheat conductivity, and (3) extremely nonuniform in organization. Inother words, the properties of the accumulation are just the opposite ofthose of metal. Therefore, it can be naturally anticipated that, when acurrent is supplied directly to the powdery or granular accumulation,the current-passing phenomena are greatly different from those in ametallic conductor. For instance, the metal is highly homogeneous inorganization and uniform in resistance distribution. Accordingly, in themetal, the current density is uniform all through the metal and thecurrent is diffused through the metal with a lapse of time. On thecontrary, since the powder or granule accumulation is exceedinglynonuniform in organization, a great local deflection is observed in eachof the electrical resistance, current density and heating value thereof,as a result of which the diffusion and assimilation of the current areobstructed in conjunction with the extremely low heat conductivity. Inmany zigzag current courses substantially in parallel which are thusproduced in the powdery and granular accumulation and which aredifferent from each other in power, a strong current course becomesincreasingly stronger with a lapse of time, and consequently adifference between the strong current course and a weak current courseis increased. Finally, all the current paths through the powdery orgranular accumulation being in contact with a pair of electrodes,concentrate to only one zigzag current course. This phenomenon is calledconcentration of electric current.

Now, the concentration of electric current is analyzed hereinafter:

The lowering rate (V) of the resistance of the powdery or granularaccumulation is proportional to the temperature-raising rate (V,) of thesame, the temperature raising rate (V,) is in turn proportional to thepower-increasing rate (V of a current, while the powerincreasing rate (Vis proportional to the firstly ,mentioned lowering rate (V) of theresistance of the powdery or granular accumulation. In other words, theabove relationships can be expressed by a formula: (V) a (V,) a (V a(V). Those factors establish the relation of cause and effect amongthemselves, and grow up through a chain-circulation.

Now, it can be understood that, when a voltage to be applied is fixed toa certain value, both the temperature of the powdery or granularaccumulation and the current density flowing through the same increasein a parabolic manner for lapse of time, i.e., in proportion to thesquare of lapse of time. In addition, the growing rate of the electriccurrent concentration phenomenon is of course proportional to theapplied voltage. It is one of the great specific features of the presentinvention that the current strength and the growing rate can beoptionally controlled. It is considered proper as supplying condition ofthe electric current from an industrial view point that a voltage of 5060 cycle/sec and 100 volt/m is applied to the powdery or granularaccumulation preheated at 800 C, and the final current density is madeto the order of 100 ampere/cm by passing the current for 30 to 60seconds. In this case, the current concentration action will not beextremely developed due to the following reasons; that is, (l) theresistance-lowering action due to temperature is saturated at a hightemperature, (2) the heat insulation character of the powdery orgranular accumulation is lowered at the high temperature. In otherwords, the cross-sectional area of the concentration of electric currentis delimited to a certain amount defined by the nature of the rawmaterial. According to an experiment as to this, when a voltage of 50cycles and 50 to 200 volt/m was applied thereto, the cross-sectionalarea of the current-passing course was from 25 cm to 35 cm. Therefore,it can be obviously utilized as a basis to plan a method and a devicefor industrializing the method of directly passing current in that thereis a limitation in the cross-sectional area of the current-passingcourse.

Now, separation of an iron component and gangue material will beconsidered in detail. In order to effect the separation of the ironcomponent and the gangue material, both heat (H) to weaken the strengthof a force combining the iron component and the gangue material and aforce (F) to detach them must be applied thereto at the same time. It iswell known that the heat (H) and the force (F) in this case, areinversely proportional to each other. Therefore, it is due to aninsufficient F, namely the effect of gravity that metal and gauguematerial are separated not only in the case of manufacturing iron butalso in the conventional method of smelting ore. Accordingly, if one canfind any force stronger than gravity, which is useful in the separationof iron from gangue material, the separation of iron from ganguematerial can be carried out even from solid ore softened slightly andfrom semi-smelted ore also, even though the ore is not completelysmelted. According to the conventional method, the following arerequired for completely smelting the raw material: obtaining rich oreand rich coal, or enriching poor ore and poor coal, heating up blowingair at a high temperature, adding heavy oil and oxygen, and providingwith a furnace member resistive against a high temperature. However, ifa method of manufacturing iron at a low temperature lower than l,000 Cin which smelting of ore is not necessary is established, all therequirements itemized above are eliminated, and therefore iron can bemanufactured at a low cost.

Now, let it be assumed that two spherical metal particles, whosediameters are A,(cm) and A (cm) respectively, are placed at an intervalof d (cm), and parallel currents of i ampere and i, ampere flow throughthe particles, respectively, as shown in FIG. 3, according toBiot-Savarts law mutual attraction forces F dyne and F dyne act on theparticles, respectively. The magnitudes of the forces are represented bythe following formulas:

F 0.02 (i i ld) A, (dyne) F 0.02 (i i /d) A, (dyne) Thus, the magnitudeof the attraction force imparted between the iron particles isproportional to the product of the magnitudes of currents flowingthrough the iron particles respectively. Therefore, when the currentdensity increasing grows up to ampere/cm at the end period of theconcentration of electric current, the magnitude of the force forseparating iron from gangue material is approximately fifteen times asmuch as that in the case of employing gravity. In addition, since theforce is in a direction of mutual attraction," this fact produces thefollowing effective actions:

(I) Electro-magnetic coagulation:

With reference to FIG. 4, when electric currents are made to flow, in adirection perpendicular to the sheet of the figure and downwardly fromabove the sheet, to

three metal particles A, B and C, respectively, mutual attraction forcesas shown by arrow marks A A B B C and C are imparted to the metalparticles, respectively. Now, assuming that the particles are movable,they move in the directions of arrow marks A I3 and C and then cometogether at a point 0. In this case, it is a common knowledge in apowder metallurgy that, if the temperature of each particle is abovetwo-thirds of its melting point, the thus concentrated particles becomea single crystal.

Thus, countless metal particles scattered in the gangue material movetowards the center among electric currents and coagulate in the form ofa metal rod whose center axis is the center line among the electriccurrents. This phenomenon will be called Electromagnetic coagulation.

Referring now to FIG. 5(A) metal particles shown by black dots andscattered in ore particles a, b, c and d are firstly coagulated intolarger metal particles as shown in FIG. 5(8). The thus coagulated metalparticles are secondarily extracted outside the ore particles as shownin FIG. 5(C). Thus, the metal particles grow up into a rod-shaped ironthrough the coagulations of the third, the fourth and so on. However, inthe case when the electro-magnetic coagulation is carried out for theraw material being agitated in the rotary kiln, the iron to be formedinto a rod is cut into pieces thereby to form granular iron.Furthermore, when a force acts in a single direction as found when usinggravity or a centrifugal force, the separation of iron from ganguematerial cannot be carried out without a furnace bottom (in case of thegravity) or a furnace wall (in case of the centrifugal force). On thecontrary, in the case of the mutual attraction force, the directions offorces are mutually opposed as shown in FIG. 6, and the gangue materialitself is adapted as a supporter. Therefore, such furnace bottom andfurnace wall are not required for the separation of iron from ganguematerial. With reference to FIG. 6, there are ore particles a, b, c, andd, metal particles a and c, are shown with black dots, electro-magneticforces A and C acting on the metal particles a, and c, are shown witharrow marks, and arrow marks 8,, B D,, and D, represent the reactionsacting on the contact points of the ore particles so as to counter-actthe respective electro-magnetic forces A, and C,. Omission of the bottomor wall supporter means eliminates the need for refractory bricks. Inaddition, this makes it possible to manufacture iron by a rotary kiln,though its has been limited in the past due to the corrosion occurringin the refractory bricks and to the adhesion of slag, and amass-production mechanism employing an endless belt, which can be usedonly in the case of a non-ore-smelting process, can be utilized formanufacturing iron.

Now, the automatic control for supplying an electric current to the rawmaterial, will be considered.

After all the reduction metal particles contained in the raw materialhave been extracted, the electrical resistance of dross material israpidly increased. Therefore, at the same time as the extractionof themetal, the current flowing in the dross material is automaticallystopped. This fact is one of the reasons by which the non-ore-smeltingmethod can be established. Thus, according to the present invention,metal contained in powdery or granular ores can be completely extracted,while no current flows to particles formed into dross material. Thosespecific features can be effectively utilized for manufacturing iron.Therefore, even if poor ore and poor coal are used as the raw materialwithout being enriched, a method of economically manufacturing iron canbe obtained.

According to the present invention, the current made to flow in the rawmaterial in order to reduce or to heat the ore can be used as it is, forthe electro-magnetic force action also, and the reduction is scarcelycompleted when the separation of iron from gangue material also iscompleted.

Hereinafter, a specific device in accordance with the present inventionwill be described.

For supplying an electric current directly to the powdery or granularraw material according to the present invention, it is required topreheat the powdery or granular accumulation so as to reduce itsspecific resistance. It is a first problem how to preheat the powdery orgranular accumulation. When the current is made to flow through the thuspreheated raw material, the current density becomes condensed partially(forming zigzag courses). However, the growing period of time (tocomplete the reduction and the separation of iron from gangue material)is relatively short (30 to 45 seconds), and the sphere (thecross-sectional area of the zigzag course) where the concentration ofthe electric current is produced is narrow in area (25 to 35 cm).Accordingly, in order to improve the yield thereof, the current must bemade to flow through the raw material little by little. This method ofsupplying the current thereto is a second problem. v v

Next, by means of the concentration of electric current the iron isseparated from the gangue material and the current flowing into thedross material is automatically ceased, but the current is still keptflowing into the powdery or granular iron or into the rod-shaped iron.It is a third problem how to interrupt this large current.

Finally, the temperature of the granular iron and the rod-shaped ironseparated from the gangue material is considerably high (approximatelyl,00,0 C.). Therefore, when the iron comes in contact with oxidizablegas, their surfaces are oxidized. It is a fourth problem how to preventthis phenomenon.

In the first problem, since the preheating temperature is relatively low(850 C in maximum), the combustion heat of a volatile substance producedthrough the dry distillation of granular coal and CO gas producedwithout fail in the reduction of the iron ore with coke, should beutilized for the preheating heat. In other words, air should besufficiently furnished to the preheating zone thereby to burn and removeP, S, As and the like from the raw material.

The fourth problem can be solved by putting into water the granular ironand the rod-shaped iron delivered from the furnace and then introducingthe steam produced. thereby into the furnace so as to effect aheat-exchange with the raw material present in the furnace.

With regard now to the second and the third problems, there are twomethods to solve the problems: One is a method (A) in which an electriccurrent is made to flow through the raw material being agitated, on thebasis of the principle that no current flows to the dross material. Theother is a method (B) in which an electric current is made to flowthrough the thin and long granular accumulation whose cross-sectionalarea is in the order of 25 to 35 cm, on the basis of the principle thatunder the concentration of an electric current the current does notsubstantially flow.

The condition common to both methods (A) and (B) is that intermittentcurrent flows and that the current is made to flow into the same portionfor about 30 to 45 seconds and is then interrupted.

In addition, in order to increase the iron production quantity, thedistance between electrodes should be increased in the method (A), whilethe number of the granular accumulations cut slenderly and atransferring rate of the accumulation should be increased in the method(B). Accordingly, a rotary kiln is best suitable for the method (A) anda tunnel kiln having an endless caterpillar belt therein is bestsuitable for the method (B).

In the inclination type cylindrical electrical rotary kiln, there is nolimitation in length, and both a preheating section and aniron-manufacturing section can be provided in one furnace. On the otherhand, though the concentrative current flowing course is limited in itscross-sectional area, the course has no limitation in length. Therefore,if the direction of the currentflowing course is coincided with thedirection of the furnace axis, the iron production quantity per oneflowing of an electric current can be increased. Moreover, if the rawmaterial inside the furnace is maintained in agitation by frictionproduced between the raw material and the inside wall surface of thefurnace, while a desired rotating speed of the furnace is maintained,the inside wall surface of the furnace and the raw material continue anintermittently contacting motion with each other.

FIG. 7 shows a cross-sectional view or a rotary kiln to illustrate theabove-mentioned .intermittently contacting motion. In this figure,reference symbol 7-] is for a furnace shell, 7-2 for an inside wallsurface, 7-3 for powdery or granular raw material, 7-4 for the rotatingdirection of the kiln, and 7-5 for grounding.

As apparent from FIG. 7, the raw material inside the kiln repeats anagitating motion due to the rotating motion of the kiln. Now, withregard to the contact conditions between the inside wall surface of thekiln and the bottom surface of the raw material accumulationwhich iscrescent-shaped in its cross-section, a part of the accumulation whichcomes in contact with the inside wall surface at a point (a) is kept incontact with the inside wall surface until the part reaches a point (b),i.e., a contact point where a tangential line 7-6 perpendicular to theearth touches the inside wall surface. The part of the accumulationcollapses when it passes the point (b). In this case, a period of timerequired for the part to move from the point (a) to the point (b) isapproximately 20/ rpm. (second). Therefore, the required time will be 40seconds in case of r.p.m.=%, and is equivalent to the growing time ofthe concentration of an electric current, described previously.

However, in case of an industrial embodiment the present invention, theinside diameter of the rotary kiln should be at least 4 meters.Accordingly, the crosssectional area of the crescent-shaped accumulationof powdery or granular raw material will be at least 2.5 m 25,000 cm formaintaining proper the raw-materialsupplying conditions. However, by theconcentrative electric-current-passing action there is produced only onethin electric-current passing course of 25 to 30 cm in theabove-mentioned extremely large sectional area during a time period of120 rotation /5 rotation. This is not economical in the operation of therotary kiln. Therefore, it is preferred so as to simultaneously multiplythe number of the electric current passing courses therein that, asshown by reference number 7-7 of FIG. 7 and 8-15 of FIGS.8(A) and 8(8),substances which are in the form of stepping-stones or steppingislandsand which are made of matter such as carborundum brick or graphite brickbeing much lower in specific resistance than of the powdery or granularraw material, are provided at proper intervals on an inside wall surfacebetween two adjacent electrodes. In other words, when thesestepping-stones are buried in the powdery or granular accumulation,several (any desired number of) successive electric-current-passingcourses are produced in parallel with one another. The coursesrespectively lie on minimum distances between both electrodes connectingthe stepping-stones and the powdery or granular accumulation in series,and are particularly low in electric resistance. Consequently, anydesired number of electric-current-passing courses can be produced inthe same accumulation at the same time.

FIG. 8(A) is a longitudinal section view taken along the central axis ofa tubular electrical rotary kiln which is broadly divided into twosections, namely, a preheating section (I) and an iron-manufacturingsection (II). The rotary kiln comprises a tubular kiln body 8-1containing the powdery or granular raw material 8-2, a hopper 8-3supplying the raw material into the kiln and an air-supplying pipe 8-4.The air-supplying pipe 84 is adapted to supply air into the kiln, andwith the aid of the thus fed air both inflammable gas and poisonous gas(S, P, As and the like) produced from the raw material are burnt andremoved, and further the heat obtained by the combustion of said gasesis utilized for preheating the raw material. Annular electrodes 8-5 madeof carborundum are adapted to reduce and coagulate the iron componentcontained in the raw material positioned between the adjacentelectrodes, thereby to separate the iron from the gangue material. Apool 8-6 is provided for cooling down the separated granular iron andthe gangue material. Various arrow marks indicate the flowing directionsof respective gases. Reference symbol 8-7 shows a funnel, 8-8 showsground and 8-9 shows an oil burnner provided for assisting in heating,in the case of starting the operation of the kiln and in other cases.

In such device, if the combustion is adjusted so as to maintain thetemperature of gas inside the kiln at 850 C maximum, the raw materialpasses through the interior of the kiln in a solid state; during whichboth the reduction and the separation of iron from gangue material iscompleted by supplying the electric current directly to the raw materialso that the raw material is changed into pumice-like slag containingvirtually no iron component, and granular iron of a large size (82percent: more than 5 mm in grain size, 9 percent: 5 to 3 mm, 8 percent:less than 3 mm), and falls into the pool so that the heat maintainedthereby is exchanged with evaporation heat.

Shown in FIG. 8(B) is a part of the longitudinal section view of thetubular electric rotary kiln, where electric power is supplied to theelectrodes.

A ring collector 8-10 made of metal is insulated from the tubular kilnbody 8-] by means of an electrically insulative support 8-13. The ringcollector 8-10 is connected to the annular electrode 8-5 through ametallic connecting bar 8-14 insulated electrically from the tubularkiln body 8-1. A brush 8-11 made of graphite is slidably arranged incontact with the outside of the ring collector 8-10. Each brush 8-11 isconnected to a power supply through an electric wire 8-12.

When this electric current is cut by the agitating action as shown inFIG. 7, sparks may occur between the thus cut portions. However, strongsparks are not caused at any portion, because the cutting action due tothe agitating action is carried out among countless particles andfurther there are a number of courses in the accumulation in contactwith both annular electrodes. Productivity of iron can be improved byincreasing distance and number of stepping stone courses between bothelectrodes, the number of electrodes, or the applied voltage.

Described hereinafter is the tunnel kiln in which a caterpillar typeendless belt is built.

In this device, the combustion heat produced when both CO gasnecessarily produced from the raw material in the process of reductionand gas necessarily evaporated from the raw material in the process ofpreheating are burned with air, is utilized for preheating, and both.Ioule heat and electromagnetic force are, utilized for the reductionand the separation of iron from gangue material. I

In order to heat by the combustion heat the powdery or granularaccumulation having a heat-resistive property and being stationary, itis necessary to make the thickness of the accumulation as thin aspossible and to heat the thus formed accumulation from both a front anda rear surface thereof.

In this embodiment, firstly the endless belt made of metal is preheatedby the combustion heat of CO gas produced during the reduction process,then the powdery or granular raw material is thinly spread over the thuspreheated endless belt. Further air is fed into the inflammable gasproduced from the thin accumulation, and finally the combustion heatproduced by burning the gas is adapted to heat the thin accumulationfrom its surface. At the same time sulphur, phosphorus and the like areremoved during combustion. H

In order to supply an electric current to every part of the wholeaccumulation by supplying the current directly to the powdery orgranular accumulation being kept stationary, the cross-sectional areaperpendicular to a direction of the current flowing through theaccumulation should be 25 to 35 cm, on the basis of the previouslymentioned principle that"an electric current concentrating action is notexceedingly advanced. The reason for this resides in that thecrosssectional area of the concentrative current flowing course whichcan be industrially produced in the accumulation of the powdery orgranular raw material by supplying an electric current having acommercial frequency and a commercial voltage directly to said rawmaterial, is 25 to 35 cm.

With reference now to FIG. 9, an endless belt 9-2 made of metal isdriven by a pulley 9-1 connected to a driving means (not shown), and thepowdery or granular raw material is thinly spread on the endless belt.In the case of preheating the thus formed thin accumulation of the rawmaterial with combustion heat, the thin accumulation moving towards thedirection of an arrow mark 9-4 can be heated from above and below.However, in case of supplying the electric current directly to the thinaccumulation, it is unknown where the electric current flowing coursesare produced. Accordingly, it is necessary to divide the thinaccumulation into small pieces and to forcibly produce the concentrationof electric current in each of the small pieces.

A rectangular hexahedron having a section abcd as shown in FIGS. 9(A)through 9(F) represents such a piece.

A unit current flowing region in the case of supplying the current in adirection (A) can be obtained, if the area of the section abcd is madeto be 25 to 35 cm. A crucible made of ceramic, which employs theabovementioned unit electric current flowing region as its internalvolume and which is of a rectangular hexahedron type with one open planeis prepared. Furthermore, electrodes are provided on both ends of thecrucible thereby to compose a unit crucible. Shown in FIG. 9(B) is theunit crucible. The kiln body made of ceramic is provided with theelectrodes 9-7 made of graphite at its opposed ends in a longitudinaldirection, and the powdery or granular raw material 9-6 is filled insidethe unit crucible. By connecting a number of unit crucibles with hinges9-8 inthe form of an endless belt as shown in FIG. 9(G), a device formanufacturing iron which moves slowly can be obtained. 7

Shown in FIG. 10 is a device for manufacturing iron, which consolidatesin series a tunnel kiln inside which an endless belt for preheating isprovided and a tunnel kiln inside which a caterpillar type endless beltfor manufacturing iron is provided. In FIG. 10,a section including theendless belt having a center line A-B is a preheating device, while asection including the caterpillar type endless belt having a center lineC-D is a device for manufacturing iron. First of all, the function ofthe preheating device will be explained hereinafter] in the preheatingsection comprises ,a ceiling wall.

10-51, a bottom wall 10-52, a gas-exhaustingfunnel 10-6, nozzles 10-7to, supply air, a feeding hole l-0-8 through which the raw material istransferred to the iron-manufacturing section, and a gas-flowing hole10-9 through which excessive CO gas flows out of the iron-manufacturingsection.

The powdery or granular raw material on the endless belt is preheatedfrom below the endless belt which is heated up by both the gasevaporated from the raw material by the air supplied through the nozzle10-7 and the gas produced through the combustion of excessive CO gassupplied from the iron-manufacturing section. It goes without sayingthat the thin accumulation of the powdery or granular raw material 10-3is preheated from its surface also.

Described below is the function of the ironmanufacturing section. Thetunnel kiln of the-ironmanufacturing sectioncomprises a ceiling wall10-151 and a bottom wall 10-152. Inside the tunnel kiln, a caterpillartype endless belt consisting of a number of unit crucibles 10-11connected'in the form of an endless belt is arranged in cooperation withsprocket. wheels 10-12. Each of the unit crucibles is provided with apair of electrodes on the inside surfaces opposed perpendicularly' tothe moving direction ofthe unit crucibles, respectively. Moreover, onthe ceiling wall, a number of stationary electrodes 10-14 made ofgraphite and provided with lead wires 10-17 to the power supply, re-

spectively, are installed so as to slidably come in contact with movableelectrodes -16 provided on both ends of each of the unit crucibles 10-11being moved. in such device, the preheated powdery or granular rawmaterial 10-3 is successively fed into each of the unit cruciblesthrough the raw material feeding hole 10-8, and there an electriccurrent is fed directly to the raw material through said stationaryelectrodes 10-14 and movable electrodes 10-16. The powdery or granularraw material which has been subjected to the action of reduction and theaction of the separation of iron from gangue material by this directsupplying of the electric current is separated into a bare-rod-shapediron and pumice-like slag, and then the bare-rod-shaped iron and thepumice-like slag are transferred out to the pool 10-19 through thedischarge hole 10-18. In addition, reference symbol 10-20 indicatesground in FIG. 10.

I claim:

1. A device for preheating powdery or grannular iron ore, said deviceadapted for use with an iron manufacturing system and comprising:

a tunnel kiln;

an endless belt made of metal elements mounted for movement within saidtunnel kiln;

means extending through said tunnel kiln at a first end thereof todeposit a thin layer of said powdery or grannular iron ore on the uppersurface of said endless belt;

passage means extending into said tunnel kiln for supplying theretoheated gas from said iron manufacturing system for preheating saidendless belt at both the upper and lower surfaces thereof,-therebythoroughly preheating said thin layer of powdery or granular iron ore;and

discharge means at a second end of said tunnel kiln for discharging saidpreheated powdery or grannular iron ore from said tunnel kiln to saidiron manufacturing system.

2. A device as claimed in claim 1, further comprising at least onenozzle means extending into said tunnel kiln for supplying theretocombustion means for aiding in the preheating of said thin layer ofpowdery or grannular iron ore.

3. A device for manufacturing iron from powdery or grannular iron ore,said device comprising a longitudinal support structure;

an endless belt formed of a plurality ofjoined individual ore carryingmeans, said endless belt being mounted for movement longitudinally withrespect to said support structure;

each of said ore carrying means comprising a refractory crucible in theshape of a rectangular hexahedron with one open plane forming an orecarrying chamber therein, said crucibles being mounted to form saidendless belt with said ore carrying chambers thereof facing outwardly;

means positioned adjacent a first end of said endless belt for supplyingsaid powdery or grannular iron ore to said ore carrying chambers;

each of said crucibles having at least one electrode integral therewithand in contact with said powdery or grannular material in said orecarrying chamber thereof;

at least one electrode mounted on said support structure and adapted tobe connected to a source of high density electric current for contactwith each of said electrode of said crucibles when said endless beltmoves longitudinally of said support structure;

whereby high density electric current is applied to said powdery orgrannular iron ore in each of said crucibles, thus separating the ironand gangue material in said ore; and

discharge means for discharging said separated iron and gangue materialfrom said crucibles.

4. A device as claimed in claim 3, wherein each of said crucibles isformed of a ceramic.

5. A device as claimed in claim 3, wherein each of said electrodes ofsaid crucibles is formed of carbon brick.

6. A device as claimed in claim 3, wherein each of said electrodes ofsaid crucibles is formed of carborundum brick.

7. A device as claimed in claim 3, wherein each of said crucibles has aseparate electrode on opposite ends thereof transverse to thelongitudinal direction of said endless belt.

8. A device as claimed in claim 7, wherein said at least one electrodemounted on said support structure comprises a plurality of electrodesets, said electrode sets being spaced in the longitudinal direction ofsaid support structure.

9. A device as claimed in claim 8, wherein each of said electrode setscomprises a pair of electrodes, one of each of said pair beingpositioned to contact one of said separate electrodes of each of saidcrucibles.

10. A system for preheating powdery or grannular iron ore andmanufacturing iron thereform, said system comprising:

A. a device for preheating said powdery or grannular iron ore, saiddevice comprising a tunnel kiln;

a first endless belt made of metal elements mounted for movement withinsaid tunnel kiln;

means extending through said first tunnel kiln at a first end thereof todeposit a thin layer of said powdery or grannular iron ore on the uppersurface of said first endless belt;

passage means extending into said tunnel kiln for supplying theretoheated gas for preheating said endless belt at both the upper and lowersurfaces thereof, thereby thoroughly preheating said thin layer ofpowdery or grannular iron ore; and

discharge means at a second end of said first tunnel kiln fordischarging said preheated powdery or grannular material from said firsttunnel kiln; and

B. a device for manufacturing iron from said preheated powdery orgrannular iron ore, said device comprising:

a longitudinal support structure;

a second endless belt formed of a plurality of joined individual orecarrying means, said second endless belt being mounted for movementlongitudinally with respect to said support structure;

each of said ore carrying means comprising a refractory crucible in theshape of a rectangular hexahedron with one open plane forming an orecarrying chamber therein, said crucibles being mounted to form saidsecond endless belt with said ore carrying chambers thereof facingoutwardly;

means positioned adjacent a first end of said second endless belt forreceiving said preheated powdery or grannular iron ore from saidpreheating device and supplying said preheated ore to said ore carryingchambers; each of said crucibles having at least one electrode integraltherewith and in contact with said powdery or grannular material in saidore carrying chamber thereof; at least one electrode mounted on saidsupport structure and adapted to be connected to a source of highdensity electric current for contact with each of said electrodes ofsaid crucibles when said second endless belt moves longitudinally ofsaid support structure; whereby high density electric current is appliedto said powdery or grannular iron ore in each of said crucibles, thusseparating the iron and gangue material in said ore; I discharge meansfor discharging said separated iron and gangue material from saidcrucibles; and passage means extending from said support structure tosaid passage means extending into said structure to supply heated gasfrom within said support means to said tunnel kiln. l l. A system asclaimed in claim 10, further comprising at least one nozzle meansextending into said tunnel kiln for supplying thereto combustion meansfor aiding in the preheating of said thin layer of powdery or grannulariron ore.

12. A system as claimed in claim 10, wherein each of said crucibles isformed of a ceramic.

13. A system as claimed in claim 10, wherein each of said electrodes ofsaid crucibles is formed of carbon brick.

14. A system as claimed in claim 10, wherein each of said electrodes ofsaid crucibles is formed of carborundum' brick.

15. A system as claimed in claim 10, wherein each of said crucibles hasa separate electrode on opposite ends thereof transverse to thelongitudinal direction of said second endless belt.

16. A system as claimed in claim 15, wherein said at least one electrodemounted on said support structure comprises a plurality of electrodesets, said electrode sets being spaced in the longitudinal direction ofsaid support structure.

17. A system as claimed in claim 16, wherein each of said electrode setscomprises a pair of electrodes, one of each of said pair beingpositioned to contact one of said separate electrodes of each of saidcrucibles.

* t a: I

2. A device as claimed in claim 1, further comprising at least onenozzle means extending into said tunnel kiln for supplying theretocombustion means for aiding in the preheating of said thin layer ofpowdery or grannular iron ore.
 3. A device for manufacturing iron frompowdery or grannular iron ore, said device comprising a longitudinalsupport structure; an endless belt formed of a plurality of joinedindividual ore carrying means, said endless belt being mounted formovement longitudinally with respect to said support structure; each ofsaid ore carrying means comprising a refractory crucible in the shape ofa rectangular hexahedron with one open plane forming an ore carryingchamber therein, said crucibles being mounted to form said endless beltwith said ore carrying chambers thereof facing outwardly; meanspositioned adjacent a first end of said endless belt for supplying saidpowdery or grannular iron ore to said ore carrying chambers; each ofsaid crucibles having at least one electrode integral therewith and incontact with said powdery or grannular material in said ore carryingchamber thereof; at least one electrode mounted on said supportstructure and adapted to be connected to a source of high densityelectric current for contact with each of said electrode of saidcrucibles when said endless belt moves longitudinally of said supportstructure; whereby high density electric current is applied to saidpowdery or grannular iron ore in each of said crucibles, thus separatingthe iron and gangue material in said ore; and discharge means fordischarging said separated iron and gangue material from said crucibles.4. A device as claimed in claim 3, wherein each of said crucibles isformed of a ceramic.
 5. A device as claimed in claim 3, wherein each ofsaid electrodes of said crucibles is formed of carbon brick.
 6. A deviceas claimed in claim 3, wherein each of said electrodes of said cruciblesis formed of carborundum brick.
 7. A device as claimed in claim 3,wherein each of said crucibles has a separate electrode on opposite endsthereof transverse to the longitudinal direction of said endless belt.8. A device as claimed in claim 7, wherein said at least one electrodemounted on said support structure comprises a plurality of electrodesets, said electrode sets being spaced in the longitudinal direction ofsaid support structure.
 9. A device as claimed in claim 8, wherein eachof said electrode sets comprises a pair of electrodes, one of each ofsaid pair being positioned to contact one of said separatE electrodes ofeach of said crucibles.
 10. A system for preheating powdery or grannulariron ore and manufacturing iron thereform, said system comprising: A. adevice for preheating said powdery or grannular iron ore, said devicecomprising a tunnel kiln; a first endless belt made of metal elementsmounted for movement within said tunnel kiln; means extending throughsaid first tunnel kiln at a first end thereof to deposit a thin layer ofsaid powdery or grannular iron ore on the upper surface of said firstendless belt; passage means extending into said tunnel kiln forsupplying thereto heated gas for preheating said endless belt at boththe upper and lower surfaces thereof, thereby thoroughly preheating saidthin layer of powdery or grannular iron ore; and discharge means at asecond end of said first tunnel kiln for discharging said preheatedpowdery or grannular material from said first tunnel kiln; and B. adevice for manufacturing iron from said preheated powdery or grannulariron ore, said device comprising: a longitudinal support structure; asecond endless belt formed of a plurality of joined individual orecarrying means, said second endless belt being mounted for movementlongitudinally with respect to said support structure; each of said orecarrying means comprising a refractory crucible in the shape of arectangular hexahedron with one open plane forming an ore carryingchamber therein, said crucibles being mounted to form said secondendless belt with said ore carrying chambers thereof facing outwardly;means positioned adjacent a first end of said second endless belt forreceiving said preheated powdery or grannular iron ore from saidpreheating device and supplying said preheated ore to said ore carryingchambers; each of said crucibles having at least one electrode integraltherewith and in contact with said powdery or grannular material in saidore carrying chamber thereof; at least one electrode mounted on saidsupport structure and adapted to be connected to a source of highdensity electric current for contact with each of said electrodes ofsaid crucibles when said second endless belt moves longitudinally ofsaid support structure; whereby high density electric current is appliedto said powdery or grannular iron ore in each of said crucibles, thusseparating the iron and gangue material in said ore; discharge means fordischarging said separated iron and gangue material from said crucibles;and passage means extending from said support structure to said passagemeans extending into said structure to supply heated gas from withinsaid support means to said tunnel kiln.
 11. A system as claimed in claim10, further comprising at least one nozzle means extending into saidtunnel kiln for supplying thereto combustion means for aiding in thepreheating of said thin layer of powdery or grannular iron ore.
 12. Asystem as claimed in claim 10, wherein each of said crucibles is formedof a ceramic.
 13. A system as claimed in claim 10, wherein each of saidelectrodes of said crucibles is formed of carbon brick.
 14. A system asclaimed in claim 10, wherein each of said electrodes of said cruciblesis formed of carborundum brick.
 15. A system as claimed in claim 10,wherein each of said crucibles has a separate electrode on opposite endsthereof transverse to the longitudinal direction of said second endlessbelt.
 16. A system as claimed in claim 15, wherein said at least oneelectrode mounted on said support structure comprises a plurality ofelectrode sets, said electrode sets being spaced in the longitudinaldirection of said support structure.
 17. A system as claimed in claim16, wherein each of said electrode sets comprises a pair of electrodes,one of each of said pair being positioned to contact one of saidseparate electrodes of each of said crucibles.